Dual pressure relief valve system



June '13, 1967 DUAL PRESSURE RELIEF VALVE SYSTEM Filed April 16, 1965 2 Sheets-Sheet 1 F|G.| INVENTOR.

JOHN B. KElR ATTORNEYS June 13, 167 J. B. KEIR 3,324,881

DUAL PRESSURE RELIEF VALVE SYSTEM Filed April 16, 1965 2 Sheets-Sheet 2 3 FIG. 4 8

J N VEN TOR.

United States Patent Delaware Filed Apr. 16, 1965, Ser. No. 448,613 8 Claims. (Cl. 137-596.13)

This invention relates to power transmissions and is particularly applicable to those of the type comprising two or more fluid pressure energy translating devices, one of which may function as a pump and another as a fluid motor.

The invention is generally concerned with a hydraulic power transmission system for controlling a plurality of motors at different pressures and more particularly with a multiple, directional control valve bank system for controlling a plurality of motors at different operating pressures.

Multiple valve bank systems have been widely used in mobile road machinery and agricultural applications and comprise a plurality of directional control valves in a side-by-side realtionsh-ip having therein any desirable combination of singleand double-acting valve spools for controlling singleand double-acting motors, such as exemplified by the patents to Berglund, No. 2,289,567, which issued July 14, 1942, and to Twyman, No. 2,247,- 140, which issued June 24, 1941.

Improvements of such systems are exemplified in the patent to James Robinson, No. 2,489,435, and the patent to Ernst F. Klessig, No. 3,077,901, both patents disclosing multiple valve bank systems having a dual function, flow control and pilot valve actuated, balanced-type relief valve incorporated in the system. Pat. No. 2,489,435 discloses a main relief valve having a separate pilot valve for controlling the operating pressure of the system; and Pat. No. 3,077,901 discloses a main relief valve of the substantially balanced type having an integral pilot valve mounted therein for controlling operating pressure of the system.

In both of such multiple valve bank systems, the maximum operating pressure of all motors in the hydraulic power transmission system would be the same, as determined by the loading of the single pilot valve operated main relief valve. There are, however, many hydraulic power transmission systems having a plurality of hydraulic motors wherein it is desirable to have a high operating pressure for one motor and a substantially lower operating pressure for another motor or motors in the system, for example, in lift trucks or front-end loaders or loading buckets, when it is desirable to hoist or raise the load device at high operating pressure but have the tilting operation of the same at a much lower operating pressure.

It is, therefore, an object of this invention to provide for a hydraulic power transmission system having a plurality of motors requiring different operating pressures, an improved and simplified dual pressure relief valve system.

It is a further object of this invention to provide an improved control valve system which is completely adequate to meet a greater variety of hydraulic applications, particularly as to requirements for dual operating pressures.

It is still another object of this invention to provide an improved multiple, directional valve bank control system which provides all of the advantages of the prior art types, and in addition, provides a dual pressure relief valve function.

It is a further object of this inventtion to provide a multiple valve bank control system having incorporated therein a pilot valve controlled, main relief valve of the balanced type, and an auxiliary pilot relief valve, preferably in cartridge form associated with the directional control valves of the bank in such a manner that the main relief valve is enabled to operate at a high pressure when one of the control valves of the system is operated and enables the same relief valve to operate at a relatively lower pressure when another directional valve in the system is operated.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a sectional view taken on line 1-1 of FIGURE 3 illustrating a hydraulic multiple valve bank control system embodying a preferred form of the present invention.

FIGURE 2 is a partial sectional view, on an enlarged scale, of a portion of the valve bank control system shown in FIGURE 1.

FIGURE 3 is a sectional view taken on line 3-3 of FIGURE 1.

FIGURE 4 is a diagrammatic view of a hydraulic power transmission system embodying a preferred form of the present invention.

Referring now to FIGURES 1 and 3, there is shown a hydraulic. multiple valve bank, directional control sys-.

tern, indicated generally by the numeral 10, comprising two directional control valve housing sections 12 and 14 held together in the usual manner by a plurality of bolts 16. The housing section 12, which will be referred to as an inlet section, has a longitudinal bore 18 within which is shiftably mounted a directional control valve spool 20 for controlling a double-acting motor and which has a stem 22 extending from the housing for manually, selectively operating the same. The inlet section 12 is provided with external connection ports, shown in FIGURE 3, which are a pressure delivery or inlet supply port 24, adapted for connection to a fluid pump, and utilization or motor ports 26 and 28, adapted for connection to a double-acting motor. Thus, the multiple valve bank control system 10 may be incorporated in a hydraulic power transmission system, shown in FIGURE 4, comprising a pump 11 driven by a prime mover, not shown, which is connected by a supply line 13 to a tank 15 and by a pressure delivery conduit 17 to the pressure delivery port 24 of housing inlet section 12. Motor ports 26 and 28 of inlet section 12 are, respectively, connected by conduits 19 and 21 to opposite ends of a double-acting motor 23.

The valve section 14, which will be referred to as an outlet section, is provided with a longitudinal bore 30 within which is shiftably mounted a directional control valve spool 32 having a stem 34 extending from the housing, the valve spool being of the type for controlling the operation of a single-acting motor. The outlet section 14 is provided with an external connection return or tank port 36 and also with external connection utilization or motor ports 38 and 40 (shown in FIGURE 4), port 38 being adapted to be connected by a conduit 39 to the raise or lift port of a single-acting motor 41, while, the motor port 40, which in conventional, multiple valve bank system would be closed by a suitable plug, has connected thereto a flexible hose 42, the opposite end of which is connected to a relief valve, pilot valve cartridge assembly 44, shown on an enlarged scale in FIGURE 2, for a purpose hereinafter explained. Tank port 36 of outlet section 14 is connected to tank 15 by a conduit 43, The motors 41 and 23 may be respectively connected to a load device to be raised and tilted, such as in a lift truck or the bucket of a front-end loader, the motor 41 being adapted to be operated under a relatively higher pressure than the operating pressure of motor 23.

It should be understood that with valve banks of the type disclosed, any number of intermediate valve sections may be placed in the bank between the inlet and outlet sections; and valve spools for controlling either singleor double-acting motors may be placed in any of the intermediate valve sections, it merely being necessary to close one of the motor ports of any valve section in which is mounted a directional control valve spool of the type disclosed for controlling a single-acting motor. It should also be understood that the intermediate sections will be eliminated, as shown, where only two fluid actuated devices are to be controlled.

The pressure delivery port 24 in the inlet section 12 is connected by a flared, cored recess 46 to a pressure delivery passage 48 which extends through housing 12, the opening on the opposite face of which is adapted to register with the opening of a pressure delivery passage 50 in outlet section housing 14 and having a closed end therein.

Each section is provided with a check valve bore spaced apart from the directional valve bore in its associated housing, the inner ends of which are intersected by the pressure delivery passage in its respective section. Only one of said check valve bores is shown in dotted lines in the inlet section 12 by the numeral 52. For the purpose of convenience, the check valve which is adapted to be mounted in the bore 52 has not been shown; but it should be understood that when mounted in bore 52 and in the check valve bore of the outlet section 14, not shown, they open upwardly to connect the said check valve bores to a pressure port 54 of directional valve bore 18 and a pressure port '56 of directional valve bore 30. The check valve bores are adapted to be closed at one end thereby by plugs, the one shown being indicated by the numeral 57.

Each directional valve bore is provided with utilization or motor ports 58 and '60 on opposite sides of its associated pressure port and which independently lead to their respective external connection utilization or motor ports and are also provided with return ports 62 and 64 spaced apart, respectively, from their utilization or motor ports 58 and 60. Two return passages 66 and 68 are formed in each housing to form two common return passages for the system, which passages respectively connect with cored return passages 70 and 72 in outlet section 14, the latter passages merging with a single return or tank passage 74 leading to the external connection tank or return port '36. The return passages 66 and 68 in each housing are connected, respectively, to the valve bore return ports 62 and 64 in said housings.

There is also provided a common by-pass unloading passage which is formed as follows: each valve bore of the respective inlet and outlet housing sections is provided with spaced-apart by-pass ports 76 and 78, the bypass port 78 of inlet section 12 opening to a face of said housing to register with the opening of by-pass port 76 of outlet section 14. By-pass port 78 of housing section 14 is connected by a passage 80 to a passage 82, passage 82 in turn being connected to passage 72 which leads to the tank passage 74. As shown in FIGURE 1, passage 82 is closed at one face of the housing section 14 by a closure member 84 and is threaded at 86, ahead of its connection to passage 72, for the insertion of a threaded plug member when the closure member 84 is removed, for the purpose of connecting thereto and controlling an auxiliary motor by a controlled flow through unloading or by-pass passages 76 and 78. When it is not desired to control an auxiliary motor by controlled byapass flow, the closure member 84 is utilized and no plug is inserted in passage 82. A by-pass passage 88 in the inlet housing section 12 connects the inlet port 24 thereof to the bypass port 76 of valve bore 18 in housing section 12.

Each directional control valve spool is provided with spaced-apart lands for closing either the by-pass port 76 or 78 and, thus, closing the common by-pass passage. Thus, the valve 20 is provided with lands 90 and 92 for respectively closing the by-pass ports 76 and 78 of valve bore 18; and the valve spool 32 is provided with lands 94 and 96 for closing the by-pass ports 76 and 78 of its associated valve bore 30. Each directional control valve spool is biased to the center position shown by a spring 98 located between retainers 100 and 102.

The valve spool 20 is also provided with spaced-apart lands 104 and 106; while, the valve spool 32 is provided with a land 108, spaced apart from land 94. In the neutral position of the valve spools shown, the pressure ports 54 and 56 of valves 20 and 32 are closed from communication with the motor ports 58 and 60 of such valves. When the valve spool 20 is shifted upwardly, the land 104, which. had blocked pressure port 54 from the motor port 60, will now open communication between said ports; while, motor port 58, which had been formerly closed from both the pressure and return ports 54 and 62, will now be connected to the return port 62. When valve spool 20 is shifted downwardly, pressure port 54 is connected to motor port 58; while, motor port 60 will be connected to return port 64.

When valve spool 32 of outlet section 14 is shifted upwardly, pressure port 56 of said valve, which had been closed from the motor port 60, is now open thereto; and when the valve spool 32 is shifted downwardly from the position shown, motor port 60, which had been blocked from return port 64, is placed in communication with said port.

Valve spool 32 is also provided with a plurality of transverse ports 59 spaced apart from a plurality of transverse ports 61 which are located in the land portion 108 of the valve spool, and which are connected to each other by an interior spool passage, indicated by the numeral 63. In the neutral position of the valve spool 32 shown, the motor port 58 is connected to the return port 62 and thus is connected to the tank passage 74 by means of the interconnection of the transverse ports 61 and 63.However, when spool 32 is shifted upwardly to connect the pressure port 56 to motor port 60 for a hoist or lift operation, the motor port 58 will no longer be vented to the return port 62 but will be closed from communication with all ports because the plurality of transverse ports 59 of the valve spool 32 has moved out of communication with the motor port 58. As the flexible hose 42 is connected to the external motor port connection 40 which leads to motor port 58 of the valve spool 32, and the opposite end of the hose connection is connected to the pilot valve cartridge assembly 44, as shown in FIGURE 4, when the single-acting valve spool 32 is in the neutral position, the cartridge valve assembly 44 will be vented through the hose connection to the valve spool motor port 58 in outlet section 14 and thence to the tank passage 74. When the single-acting spool 32 is operated for a hoist operation, the vent connection for the cartridge valve assembly 44 will be closed, and thus, the auxiliary valve assembly becomes ineffective.

Means for maintaining regulated flow rate through the unloading or by-pass passage when all the valves are in the 7 neutral position, and for by-passing or shunting the remainder of the pressure fluid supply completely around the individual valve spool members by a separate passage connected to the return passage, is provided by the mounting of a flow control valve piston, indicated generally by the numeral 110 in a bore 112 opening to a face 114 of the inlet housing section 12. The control piston 110 is provided with opposed balanced operating surfaces 116 and 118. For the purpose of connecting inlet pressure to the operating surface 116, the flared inlet recess 46 in section 12, and which is connected to the pressure delivery port 24, is not only connected to pressure delivery passage 48 but also communicates with the valve bore 112 and the operating surface 116 of the operating piston 110. A throttle 122 is placed in the inlet passage 88 beyond the connection of the flared recess 46 thereof to passage 88 to make the operating surface 116 responsive to inlet pressure ahead of the throttle 122. The throttle 122 is provided or formed in a throttling plug 124 threaded into the passage 88. The operating surface 118 is exposed to pressure beyond the throttle 122 by means of a passage 126 connected to passage 88 and by a passage 128 connected to the bore 112. Interposed in the passage 126 is a restriction 130. The operating piston 110, which performs the function of an overflow or by-pass type of flow control valve is also adapted to perform the function of a main relief valve with the cooperation of an integral pilot valve mounted therein; and the restriction 130 is adapted to cooperate in the relief valve function of the flow control valve piston 110. As shown more clearly in FIGURE 2, the operating piston 110 is provided with a passage 132 having a seat 134 therein, upon which rests a pilot valve 136 biased thereto by a spring 138. The pilot valve 136, in the position shown, closes communication between the passage 132 and a passage 140 which leads directly to an isolated exhaust passage 142. The spring 138 will determine the highest maximum operating pressure for the hoist operation of motor 41.

Pilot valve cartridge assembly 44 comprises a body or housing 144 fitted into bore 112 from the face 114 of inlet section 12, the body 144 having a passage 146 provided with a shoulder forming a seat 148 upon which is biased a second pilot valve member 150 by means of a spring 152. Passage 146 opens to a swivel connection 154 attached to which is the fluid hose member 42, the opposite end of which is adapted to be connected to motor port 40 of outlet section 14, as shown in FIGURE 4. Whereas, the spring 138 for pilot valve 136 determines the pressure at which a hoist or lifting operation by the motor 41 will be performed; the rating of spring 152 determines the lower pressure at which a tilt operation will be performed by motor 23.

With the body 144 of pilot valve cartridge assembly 44 fitted in bore 112, as shown, the inner end of the cartridge assembly is opposed to and separated from operating surface 118 of the control piston 110 within which pilot valve 136 is mounted in an opposed relation to pilot valve 150 and forms a chamber 156 between the pressure responsive operating surfaces of the pilot valves which is directly connected to the passage 128 thereby exposing both pilot valves to inlet supply pressure. Located in chamber 156 is a spring 158 which normally tends to maintain the control piston 110 in a position closing communication between the pressure delivery inlet recess 46 and the exhaust passage 142 which extends through the housing sections 12 and 14 to the return or exhaust passage 72 in outlet section 14 leading to tank passage 74.

The spring 158- normally maintains the flow control valve piston 110 to a position wherein the inlet recess 46 is closed to the isolated exhaust passage 142. As the opposed operating surfaces 116 and 118 are substantially balanced, the operating piston 110 will be shifted downwardly when a pressure drop equal to the loading of spring 158 is reached for the purpose of dumping fluid in excess of a desired regulated flow in the by-pass passage back to the tank passage through the isolated exhaust passage 142. Thus, the operating piston 110 functions to maintain the pressure drop across the throttle 122 in the by-pass passage, as determined by the loading of Spring 158, substantially constant and thus the flow through the unloading or by-pass passage at a regulated rate. However, the operating piston 110 is only effective as a flow control valve for the by-pass or unloading passage when both valves 20 and 22 are in the neutral position. When either valve spool is operated, the by-pass passage is closed to flow through the unloading passage from the inlet section to the outlet section return port and thus, there will not be a differential of pressure on the opposed operating areas of the piston 110. The operating piston 110 will continue, however, to perform the function of a main relief valve with the cooperation of either pilot valve 136 or pilot valve 150.

For a desrciption of the function and operation of control piston as a flow control valve, reference may be had to the patent to James Robinson, 'No. 2,489,435, or the patent to Ernst F. Klessig, No. 3,077,901; and for the operation of the control piston 110 as a main relief valve controlled by a pilot valve separated therefrom, Pat. No. 2,489,435, and as a main relief valve wherein the pilot valve is integral therewith, Pat. No. 3,077,901.

In order to provide a system wherein high pressure may be utilized for one motor, such as for a raise or lift operation, and a substantially lower pressure for the operation of another motor, such as for a tilt operation of the load device, a second pilot valve is added to a multiple valve bank system, such as disclosed in Pat. No. 2,489,435 and Pat. No. 3,077,901. The second pilot valve is incorporated in a cartridge assembly which is preferably fitted into a bore already occupied by the dual function, flow control and main relief valve operating piston 110. A flexible hose is connected to the exhaust chamber of the second pilot valve and to the external motor connection port of the valve housing having therein the single-acting hoist valve spool, the opposite end of the hose being connected to a motor port that would normally be plugged. It should be noted that in the system disclosed, the singleacting hoist spool may be placed in either the inlet or outlet section. A special hoist spool is provided which, in the neutral position, will connect the exhaust chamber of the auxiliary pilot valve to the tank return port 74; and for this purpose, the hoist spool is provided with the spaced-apart transverse ports 59 and 61 interconnected by the spool passage 63 for the purpose of connecting the valve bore motor port 58 to the valve bore return port 62 with the valve spool in the neutral position. The specially constructed spool, when operated to the hoist position, will close the exhaust chamber of the auxiliary pilot valve by reason of transverse ports 59 shifting out of communication with motor port 58, thus making the auxiliary pilot valve ineffective.

Thus, when the spool 20 is shifted to provide a tilt operation of motor 23, the valve spool 32 remains in neutral. If, during the tilt operation, a pressure is reached determined by the lower setting of spring 152, pilot valve 150 shifts from its seat 148 opening passage 146 to the tank port 74 in the outlet section 14 by means of hose 42, motor port 40 of outlet section 14, motor port 58 of valve bore 30, the transverse ports 59spool passage 63and transverse ports 61 of valve spool 32, return port 62, and return passage 66. When the pilot valve 150 shifts from its seat, a pressure operating diflerential is established on the opposed operating surfaces 116 and 118 of control piston 110 greater than the loading of spring 158; and the control piston 110 shifts to connect the inlet recess 46 to the exhaust passage 142 for relieving excessive pressure fluid therethrough.

When a hoist operation is being performed, the transverse ports 59 of valve spool 32 pass out of communication with motor port 58, and the exhaust chamber of pilot valve cartridge assembly 44 is no longer vented. The spring 138 of integral pilot valve 136 then determines the high operating pressure for the hoist operation. When this pressure is reached, pilot valve 136 shifts from its seat and chamber 156 is vented through the open pilot valve 136 and the seat 134 by the passage 132 to the passage and is connected to the outlet section 14 by means of passage 142 which is connected to the return or tank port 74 in section 14 by passage 72.

Thus, there is provided a hydraulic system for controlling a plurality of motors wherein the individual motors for performing different operations may be operated and controlled at diiferent pressures. The dual pressure relief valve system may be simply and economically provided in well-known multiple valve bank systems having therein a pilot valve actuated main relief valve of the balanced type simply by adding a cartridge assembly including another pilot valve to the system operating at a different pressure than the first pilot valve, and connecting the venting side of said pilot valve to the normally unused motor port of a valve section in the bank having therein a spool of the single-acting type, and which in the neutral position of such valve will vent the exhaust chamber of the second pilot valve, and when shifted to operating position, will close the vent to make the second pilot valve ineffective.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a hydraulic power transmission system having a fluid pump connected to two directional control valves which are connected to two fluid motors having different operating pressure requirements for controlling the directional operation of the same, the combination of:

(a) a main relief valve of the pilot valve controlled,

substantially balanced-type;

(b) two pilot valves operable at different maximum pressures, either of which, when operated, causes operation of the main relief valve;

(c) each pilot valve having an exhaust passage, one of which is continuously vented to a low pressure portion of the system, the other of which is connected to a motor port of one of said directional control valves;

((1) said motor polt being connected in the neutral position of said one directional valve to the low pressure portion of the system for causing said other pilot .valve to be effective, and being disconnected therefrom in an operating position of said one directional control valve for causing said other pilot valve to become completely ineffective.

2. A system as in claim 1 wherein one of said directional valves is provided with two external connection motor ports, only one of which is adapted to be connected to the motor having the highest operating pressure requirement, the other of said external connection motor ports being connected to the exhaust passage of the pilot valve which controls the lowest operating pressure requirement of the other of said motors.

3. A system as in claim 1 wherein the main relief valve and two pilot valves are mounted in one of the directional valve housings, one of said pilot valves being carried by the main relief valve, and the exhaust passage of the other pilot valve being connected to an external connection motor port in the housing of the other directional control valve.

4. A system as in claim 3 wherein the housing of said other directional control valve is provided with two external connection motor ports, only one of which is adapted to be connected to the motor having the highest operating pressure requirement, the other motor port being connected to the exhaust passage of said other pilot valve which is adapted to control the lower pressure operating requirement of the other of said motors.

5. For use in a hydraulic power transmission system having a fluid pump adapted to be selectively connected to a plurality of fluid motors, at least two of which have different maximum pressure operating requirements:

(a) a multiple valve bank comprising a plurality of housings maintained in side-by-side relationship, one of which comprises an inlet section and another an outlet section;

(h) each housing having a valve member shiftable therein for selectively controlling the operation of said motors;

(c) a main relief valve of the pilot valve controlled,

substantially balanced-type, and two pilot valves operable at the different maximum pressure operating requirements, either of which, when operated, causing operation of the main relief valve, and all being mounted in the inlet section;

(d) each pilot valve having an exhaust passage, one of which is continuously vented to a low pressure portion of the valve bank;

(e) one of said housings having two motor ports, only one of which is adapted to be connected to a motor having the higher pressure requirement, and the other of which is adapted to be connected to the exhaust passage of the other pilot valve; and

(f) means in the valve member in the said one housing for connecting, when in a neutral position, the said other motor port to the low pressure portion of the valve bank for causing said other pilot valve to be effective and for disconnecting the same when in an operating position for causing said other pilot valve to become completely ineffective.

6. A multiple valve bank as in claim 5 wherein the main relief valve carries one pilot valve in opposed relation to the other pilot valve, all being mounted in a single bore of the inlet section, said bore having an external connection port adapted to be connected to said other motor port of the said one housing.

7. A multiple valve bank as in claim 5 wherein a pump unloading passage is provided through the bank, said main relief valve also performing the function of a flow control valve and maintaining a regulated flow rate through said unloading passage when all valve members are in the neutral position.

8. A multiple valve bank as in claim 5 and comprising only an inlet section and an outlet section, one of said sections having two motor ports, one of which is adapted to be connected to the motor having the highest pressure requirement, the other being connected by a flexible hose connection to the exhaust passage of the pilot valve which is operable at the lowest operating pressure requirement, said one section having a valve member for venting in one position and closing completely in another position the exhaust passage of the low pressure requirement pilot valve.

M. CARY NELSON, Primary Examiner. 

1. IN A HYDRAULIC POWER TRANSMISSION SYSTEM HAVING A FLUID PUMP CONNECTED TO TWO DIRECTIONAL CONTROL VALVES WHICH ARE CONNECTED TO TWO FLUID MOTORS HAVING DIFFERENT OPERATING PRESSURE REQUIREMENTS FOR CONTROLLING THE DIRECTIONAL OPERATION OF THE SAME, THE COMBINATION OF: (A) A MAIN RELIEF VALVE OF THE PILOT VALVE CONTROLLED, SUBSTANTIALLY BALANCED-TYPE; (B) TWO PILOT VALVES OPERABLE AT DIFFERENT MAXIMUM PRESSURES, EITHER OF WHICH, WHEN OPERATED, CAUSES OPERATION OF THE MAIN RELIEF VALVE; (C) EACH PILOT VALVE HAVING AN EXHAUST PASSAGE, ONE OF WHICH IS CONTINUOUSLY VENTED TO A LOW PRESSURE PORTION OF THE SYSTEM, THE OTHER OF WHICH IS CONNECTED TO A MOTOR PORT OF ONE OF SAID DIRECTIONAL CONTROL VALVES; (D) SAID MOTOR PORT BEING CONNECTED IN THE NEUTRAL POSITION OF SAID ONE DIRECTIONAL VALVE TO THE LOW PRES- 